The present invention relates to a braking device inserted between a motor comprising a drive shaft and a load, comprising brake disks arranged facing each other, an| elastic means turning the disks against each other and means collaborating when the drive shaft of the motor is driven, to part the brake disks against the action of the elastic leans and for transmitting a mechanical torque from the drive shaft to a receiving shaft which rotates as one with one of the brake disks rotatably connected with the drive shaft, the receiving shaft being kinematically connected to the load.
The invention relates more specifically to a brake for a tubular motor for driving the winding tube of a roller shutter or the like.
Utility model IT-BO-92 U 000009 discloses a braking device arranged in the tube of the motor for driving the winding tube of a roller shutter or the like between the motor and a reduction gearset. The brake is in the xe2x80x9cbrakedxe2x80x9d position, preventing the winding tube from turning, when the drive shaft is stationary, and moves into the xe2x80x9cfreexe2x80x9d position, freeing the winding tube to turn when the drive shaft is driven. This brake device also has the function o transmitting mechanical torque from the motor to the reduction gearset. The braking device comprises two brake disks arranged facing each other, one of which is rotatably mounted on the shaft of the motor and ends in a pinion which meshes with the reduction gearset and has a cut-out in which a pin housed in the drive shaft can move, and the other of which is fixed to the tube of the motor. The device also comprises a compression spring between a bearing the drive shaft and the brake disk rotatable mounted on the drive shaft. When no power is applied to the motor, the action of the spring on the disk rotatable mounted on the shaft presses the disks together. Thus, with the disks locked together, the input pinion of the reduction gearset is immobilized, and the roller shutter is therefore prevented from moving. When power is applied to the motor, the drive shaft turns with respect to the brake disks initially immobilized. This rotational movement with respect to the brake disk rotatable mounted on the drive shaft will, through action of the pin on the cut-out, cause the disk to effect a translational movement against the action of the spring, causing the disks to separate. The roller shutter is therefore released. Rotational movement of the shaft with respect to the disk continues until the axial force exerted by the disk reacting to the weight of the shutter balances the force of the spring or, failing that, until the pin meets an obstacle at the end of the cut-out, and mechanical torque is therefore transmitted from the motor to 1the reduction gearset and the roller shutter is therefore given an opening or closing movement.
Such a braking device requires, in the xe2x80x9cbrakedxe2x80x9d position, a clearance between the pin and the cut-out made in the disk, guaranteeing contact between the brake disks and therefore braking. This operating clearance needs to be controlled with precision because it also determines the amplitude of the rotational movement of the shaft with respect to the disk needed to separate the brake. Now, the string of dimensions involved in this operating clearance involves the pin, the drive shaft, the bearing, the tube of the motor and the disk As the number of these components is relatively large and as some of them have relatively large dimensions, manufacture and assembly need to be performed with great care in order to obtain an appropriate tolerance band on the operating clearance. These operations are therefore expensive. In addition, such a device, because of the location of the spring, leads to axial loads in the bearing and this dictates the use of a ball bearing to carry the shaft of the motor.
The object of the invention is to produce a braking device that alleviates these drawbacks. In particular, the invention proposes to produce a braking device in which, on the one hand, the string of dimensions associated with the functional clearance between the pin and the cut-out has an overall length shorter than the one disclosed in document IT-BO-92 U 000009 and, on the other hand, the force exerted by the spring on the disk is not reacted in the bearing supporting the drive shaft.
The device according to the invention is one which comprises a juxtaposition of disks connected alternately to the drive; shaft and to a casing containing the motor by sliding connections, the end disks of the juxtaposition being connected to the drive shaft.
According to an additional feature, the end disks of the juxtaposition are rotatably connected to the drive shaft.
According to another feature, the disks are rotatably connected to the drive shaft.
According to a preferred embodiment, the braking device comprises three brake disks.
The disks rotatably connected on the shaft are advantageously in sliding connection with each other.
According to one embodiment, one of the brake disks is rotatably connected to the drive shaft has a means which, combined with another means present on the shaft, allows the disks to be parted and another of the brake disks being rotatably connected with the drive shaft is secured to the receiving shaft.
According to another embodiment, one same brake disk is rotatable connected with the drive shaft has a means which, combined with another means present on the shaft, allows the disks to be parted and is secured to the receiving shaft.
The means collaborating to part the brake disks against the action of the elastic means may comprise a pin planted in the drive shaft and a ramp made on one of the brake disks is rotatable connected with the drive shaft.